Production of safety-grounds for documents.



, C. G. PETIT.

PRODUCTION OF SAFETY GROUNDS FOR DOCUMENTS.

APPLICATION FILED OCT. 11. 1911.

,153,131 Patentedsept. 7, 1915.

in d 0 M/VE/VTW? WITNE5$E5 I CHHFLES GU/ALaUME P5717 COLUMBIA PLANOGRAPHc0.. WASHINGTON, D. c.

; rien CHARLES GUILLAUME'VEETIT, or BELLEVUE, FRANCE.

rnonncrron or sarnrr-enonnns rortnoourrnn'rs.

Specification of Letters Patent. at nted t, 7, 5,

Application filed October 11, 1911. SrialNo. 654,428. i

To all whom it may concern Be'it known that 1, CHARLES GUILLAUME PETIT,of Rue Dumont dUrville, Bellevue, Department of Seine et Oise, Republicof France, have invented certain new and useful Improvementslll'filiGPIOdllClZlOIl of Safety-Grounds for Documents, of; which thefollowing is a full, clear, and exact description. I V

This invention relates to safety-grounds for bank-notes,share-certificates and other valuable papers or documents of any kind.

It consists in reproducing by means of two or more half-tone orline-screens of different line-inclinationsor different designs and withdifferent lengths of exposure, a half-tone pattern arranged so as topresent most diverse gradations in such a way as to vary the thickeningor thinning of the lines, dots 0r grains furnished by the screens, thenforming by means of each photographic print so obtained blocks, platesor reproductions adapted to print by any usual method, and lastlyprinting the safetyground my means of the latter withcolors selected sothat decomposition of the'image obtained becomes substantiallyimpossible.

By reason of the possibility of varying at will the gradation of'thehalf-tones of the pattern and therefore the thickness of the screenedlines, dots or grains, and owing'to' the dlfierence of inclination ordeslgn of the screens, there are obtained new decorative effects whichcan be varied at will, and the reproduction of which is impossible; theinvention, therefore, offers complete protection against falsificationsor forgery.

For the preparation of the pattern serving to obtain the variablethickening or thinning of the lines, dots or grains of the screens,there is employed the following process which by reason ofitssimplicity, its low cost of. working and the guarantees againstfalsification which it presents, forms an essential part of theinvention. It consists in employing a nonactinic (black, yellow, orange,etc.)' paper or equivalent material which is perforated more orless-symmetrically to produce a design which, although coarse, may yetbe agreeable'to the eye. The perforations are formed in the paper orother material in any suitable manner, for example bymeans of a hollowpunch, but the perforations are made of diflerent sizes and of differentshapes in;

order that in the operation to be hereafter described the light may actto a greater or less degree but for the same length of time upon thesensitive preparations. The perforated paper so obtained is used like aphotographic negative which it is desired to reproduce upon sensitizedpaper; that is to Y say, it is placed in a printing-frame, but veryslightly separated from the sensitized paper by means of an intermediatesheet of clear glass. A ground glass is placed at the front of theprinting frame and the wholeis exposed to the light of the sun or of oneor more electric'lamps, taking care not to leave the frame more than afew seconds in the same position and taking away the ground glass fromtime to time. I

The intensity of the image is judgedas is usual in printing on paper, byopening the frame whenit is thought that the de-' sired effect is nearlyreached. The light passing through the perforations in the dif- Iferentpositions in which the printing frame is held under the source oflight causes an lnnumerable quantity of tones of, an original decorativeeffect, because the luminous rays falling sometimes directly, sometimesobliquely, upon the perforations produce at certain points crossings ofintense light upon the sensitive surface, while other parts are lessexposed and others again are wholly concealed. 'The whole of thisoperation with ground glass, direct light and movement of the frame andof the glass is intended to obscure or render indefinite the image ofthe perforation in such a way that sensitized paper is withdrawn fromthe Q frame, washed and fixed in the usual man- It is evident that theimageobtained ner. in the manner described can in no way berepeated asecond time, especially if theperforated paper is destroyed after asatisfactory decorative result has been obtained.

protection against falsification. The pattern thus formed is twicereproduced at different' angles by means of copying linescreens and bythe usual printing methods (copper-plate, typography, lithography,

etc), The result is obtained by means of l Consequently themethodaflords a complete a substantially differing times of exposure forthe preparation of the screened negative blocks, so that one of themreproduces the whole of the image and the other givesonly the darkhalf-tones and the blocks. In these conditions when printing takesplace, if one of the'bloclis'is printed for example in yellow and theother in red, the resulting orange will be formed only inthe dark halfIn the accompanying drawing is shown in cross section a printing frameby which the pattern may be obtained. 1

As here shown the frame F) has an inwardly projecting head at the frontin which a horizontal slot is provided to permit the temporaryadjustmentof a sheet of ground glass a. A sheet of clear glass crests against theinner face of the bead and-supports the perforated negative d. Severalsheets of clear glass 0, 6 6 separate this from this sheet f ofsensitized paper, which is held in position .by'the backof the frame 9.

The invention is not limited to the above described details ofexecution. ple, two of more difierently perforated pat- ,terns might beused and the screened or half-tone blocks obtained separately therefrommight be printed one upon the other.

Again the perforated patterns might be replaced by photographic printsor negatives or any compositions adapted to serve as such, maintained ata distance from the sensitized paper. Moreover, there may be Forexamprinted upon the safety-grounds obtained in the manner abovedescribed, either at once or at the same time as the letter-press,

any border, ornamentation or the like that may be desired as a thirdimpression.

Having thus described my invention, what I'claim' as such and desire tosecure by Letters Patent is 1. As a new article of manufacture, a

sheet of suitable material having printed thereon a safety ground of thecharacter described comprising superposed impressions of indeterminateiris-like outlines of diverse light gradat1ons,sa1d impresslons being indifferent colors and screen schemes, the

Whole forming upon the sheet an image having blended colors andindeterminate outlines practically incapable of lineal decomposltion.

'2. As a new article of manufacture, a

sheet of suitable material having printed thereon a safety ground forbank notes and the like, comprising a halftone composed of a pluralityof superposed images each of indefinite and vague, and uncertain outlinehavin li ht 'radations var in from osi- D b t) the and strong effects tovague and confused and disappearing efiects, the super.-

posedimages being differently colored and the colors effecting afinished blend.

In testimony whereof I have signed my name to this specification, in thepresence of two subscribing witnesses.

CHARLES GUILLAUME PETIT.

Witnesses: Q JACQUES LEJEUNE,

y LEON PEILLETL Copies of this patent may be obtained for five centseach, by addressing the Commissioner of Patents,

' Washington, D. Q?! A v

